In certain types of offshore drilling and hydrocarbon production, a shaft extends downward from a buoyant structure and latches into a receptacle on an anchor piling at the sea floor. Tension is applied to the shaft, which is transmitted to the anchor piling. This technique is used for connecting the bottom of a tendon of a tension leg platform to a receptacle mounted at the sea floor. This method is also used for anchoring a riser tower. For convenience, these connectors will be referred to herein as bottom tendon connectors whether used to anchor a tension leg platform, a riser tower, or other buoyant structure.
In the past, bottom tendon connectors have used a fairly lengthy receptacle at the sea floor. The shaft at the lower end of the tendon has a latch member that inserts into the receptacle and latches to the receptacle by axial positioning. In one type, the connector is inserted until the latch member is below the receptacle load interface, then lifted. In another type, the latch member is partially inserted past the load interface, then lifted. To disengage, the connector is inserted deeper into the receptacle and lifted. Another type involves rotating the connector when the connector is fully lowered in the receptacle. These prior art connectors typically require a long receptacle and significant vertical motion or rotation of the entire connector for operation.
Also, in these prior art connectors, the shaft at the lower end of the tendon is fixed relative to the connector body or housing to which it is attached. Normally the shaft will experience only tension after the connection is made up. In rare circumstances, however, due to wave motion or other factors, the tendon may drop downward sufficiently to completely eliminate the tension in the shaft. The prior art types normally do not have provisions for allowing downward movement of the shaft in the event of a momentary loss of tension in the shaft. If the shaft moves downward, it may disengage.